Will my trademarked logo protect my designs?

Hi. I am playing around with the idea of starting a business online selling designed tshirts and apparel. I've been reading extensively on the legal aspects of this endeavor, but copyright is the one issue that always confuses me. I was wondering, if I wanted to protect my artwork, would I have to copyright every single design, or would putting my trademarked logo on each of my shirts protect my designs as well? Thanks in advance